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Redoubt – the latest on the 15 March 2009 activity 17 March 2009

Posted by admin in activity reports, Alaska, Redoubt, United States.
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Redoubt 15 March 2009 (photographer Heather Bleick, AVO/USGS image)
Above: Photograph taken during observation/gas data collection flight to Redoubt Volcano on 15 March 2009. North face of Redoubt Volcano about 35 minutes after the ash burst of 15 March 2009. Dark ash stripe on crater floor visible behind ongoing vigorous vapor and gas plume emanating through the glacial ice. The dark stripe in foreground is a watery debris flow that emerged from beneath the ice about 20 minutes after the ash event. (Photographer Heather Bleick, image courtesy AVO/USGS.) [source]

By any standards, the folks at the Alaska Volcano Observatory do an excellent job of keeping everyone informed about the situation at Redoubt. Yesterday a lengthy statement was released dealing with the explosive event that occurred on the afternoon of 15 March: it can be accessed via the AVO’s Redoubt activity page, or the full text can be found at this direct link. And there is also a video of the activity, taken during an AVO overflight, giving great views into the crater and of the steam plume.

The events of 15 March are described as follows:

Seismic activity at Mount Redoubt increased at about 1:05 AKDT Sunday afternoon (March 15, 2009) and approximately 4 hours of continuous volcanic tremor ensued. The onset of the tremor was associated with a small explosion that produced a plume of gas and ash that rose to about 15,000 feet above sea level and deposited a trace amount of ash over the summit-crater floor and down the south flank of the volcano to about 3,000 feet … At this time it does not appear that the increase in activity heralds a significant eruption in the short term, but conditions may evolve rapidly.

An AVO overflight, tasked with measuring gas emissions, was in progress when the activity began, so a thorough observation was made and some wonderful pictures and a video were obtained. A new vent was observed, just south of the 1990 lava dome, producing ash emissions: ‘Although ash emission was short lived’, notes the statement, ‘it represents the first documented ash fall during the current episode of unrest at Mount Redoubt’. At this stage it is not clear whether this is new or old ash – that is, whether it originates in new magma or is pulverized old material. The AVO intends to collects ash samples for analysis later this week: it will be fascinating to see the results.

The preliminary interpretation of Sunday’s activity is that it was a phreatic explosion in the shallow hydrothermal system of the volcano: ‘Steam-driven explosions are not unexpected events at Redoubt given the amount of heat that is being released at the surface. It is possible that more such explosions can occur with little or no warning. It is possible that these plumes can reach above 20,000 feet, and may contain minor amounts of fine ash’.

As for the future, and bearing in mind that all volcanologists can ever do is forecast, never predict, the AVO has this to say:

Relatively rapid increases in seismic activity, and an overall waxing and waning pattern to the seismicity at Redoubt may persist for weeks to months. Increases in seismicity may or may not be associated with other volcanic phenomena, such as minor ash emission, and vigorous steaming. The burst of activity at Redoubt on March 15, 2009 indicates that the volcano is still in a restless condition.

The conclusion of yesterday’s AVO status report with regard to Redoubt remains valid: ‘ It does not appear at this time that a significant eruption is likely in the short term, but conditions may evolve rapidly’.

Redoubt 15 March 2009 (photographer Heather Bleick, AVO/USGS image)
Above: Photograph taken during observation/gas data collection flight to Redoubt Volcano on 15 March 2009. View is looking at the south flank of Redoubt, showing the light dusting of ash from the 15 March 2009 phreatic event. (Photographer Heather Bleick, image courtesy AVO/USGS.) [source]

Redoubt 15 March 2009 (photographer Heather Bleick, AVO/USGS image)
Above: View of the summit crater of Redoubt Volcano on 15 March 2009, about three hours after a small ash eruption through the ice cap. Continuing vigorous emission of water vapor, volcanic gas is occurring from the 1990 lava dome (dark area at lower right) and the new vent that is obscured by the plume. Ash and other tephra fall from the event is the dark material blanketing the south side of the crater. In the foreground is the dark face of the 1990 lava dome. (Photographer Christina Neal, image courtesy AVO/USGS.) [source]

For all our Redoubt coverage: Redoubt « The Volcanism Blog.

Information
Global Volcanism Program: Redoubt – summary information for Redoubt (1103-03-)
Alaska Volcano Observatory – Redoubt – AVO information and updates for Redoubt
Alaska Volcano Observatory – main page for the AVO

The Volcanism Blog